Yesterday, during a small window when deep-sea operations weren’t underway, we did a daylight plankton tow. The net was towed across depths from 200 m to the surface with a 350 µm mesh net for about 30 minutes. We recovered a bonanza of small pelagic animals and some of us spent the next few hours sorting and photographing them. This included a diversity of pteropod and heteropod molluscs (see pic).
Before we leave the Tonga Trench we are hoping to do a night plankton tow to see if we can pick up any of the animals that migrate towards the surface during the dark. While the gravity core was a spectacular success is retrieving a 2 m long core of sediment from more than 9000 m depth we were a little disappointed to find no obvious animal life in the core. We rinsed the top 12 cm of the sediment core through a 250 µm mesh sieve and sorted through it carefully but to no avail. This is not to say that there are no animals in the sediment of the trench; we might have rinsed away very small animals or the sediment may have been churned in the core and we missed the right spot for the animals. Hopefully the lander that is baited with some dead fish and octopus will trap us some deep animals from the bottom of the Tonga Trench. The sediment itself showed some spectacular variety (see pic) and we’ll be taking this back to SIO for some geologists to examine.